Getting LBNE 35-ton cryostat ready for cool-down

A 35-ton-capacity cryostat—a prototype for the proposed multi-kiloton LBNE liquid-argon far detector—stands ready for cool-down in PPD's PC-4 facility and for its first liquid-argon fill.

Workers constructed the garage-sized cryostat by welding together modular, multi-layer pieces to form a single insulated and leak-tight "membrane" similar to that planned for the LBNE far detector. Testing will begin this summer to determine whether the liquid-argon purity levels required by LBNE can be achieved and kept stable in this type of cryostat without prior evacuation. The liquid-argon purity demonstrator (LAPD), a cryostat of smaller size and different construction, reached these goals in 2012, paving the way for this LBNE prototype.

Purer liquid argon makes for cleaner detector signals, since impurities tend to "capture" electrons ionized by particle interactions—the very electrons the scientists want to detect—before they reach their destination.

Discarded practice welds for the inner stainless steel membrane and various glued insulation samples outside the cryostat reveal the complex, layered construction performed by the cryostat team, led by engineer David Montanari. A dozen or so penetrations emerge from the top of the tank for the cryogenic services that will now be deployed—the fill system, purity monitors, condenser, purification system lines, temperature sensors and safety devices—the same systems that LAPD has been using.

Engineer Terry Tope coordinates the extension of these systems to the LBNE prototype. Several switches and two critical valves, installed last year while LAPD was undergoing repairs and upgrades, will enable switching the entire system from servicing one tank to the other.

Currently Tope's team is finishing the piping hookup from the purification systems to the 35-ton cryostat and the controls work. The next step will be to purge the cryostat of air using gaseous argon, after which a mix of liquid and gaseous argon will be sprayed into the cryostat to cool the volume down to about -298 degrees Fahrenheit. At this point, the liquid from LAPD will be introduced and circulated through filters until a high purity is achieved.

If anything goes wrong during the fill, the liquid argon—worth about $30,000, according to Tope—won't be lost. It can be pumped back to LAPD while the team fixes the problem.

Once the liquid has been successfully transferred, additional liquid argon from DZero will be brought in to top off the 35-ton cryostat. Then the purity testing, coordinated by physicist Alan Hahn, will begin. Maintaining the purity level over the run is an important goal.

"We plan to adopt the same data-taking scheme that LAPD is using—every two hours we run the purity monitors and record the data," Hahn said. "This fits the time scale of purity changes, usually on the scale of a day."

The prototype is expected to provide results in about three months of running.

—Anne Heavey

In Brief

FRA scholarships awarded

Fermi Research Alliance has selected the recipients of this year's FRA Scholarship Awards. They are:

Space warps project needs your help

From Interactions.org, May 8, 2013

Astronomers are asking volunteers to help them search for "space warps." More commonly known as "gravitational lenses," these are rare systems with very massive galaxies or clusters of galaxies that bend light around them so that they act rather like giant lenses in space, creating beautiful mirages.

Anyone can participate in Space Warps project, which was launched on 8 May 2013. Visit www.spacewarps.org and spot these spectacular and rare astronomical objects using data from large astronomical surveys. Astronomy enthusiasts can partake in the discovery of these magnificent lenses and help astronomers uncover the role that dark matter plays in the formation of galaxies.

"Not only do space warps act like lenses, magnifying the distant galaxies behind them, but also the light they distort can be used to weigh them, helping us to figure out how much dark matter they contain and how it's distributed," said Dr. Phil Marshall, co-leader of the project at the University of Oxford.

Tick activity this season

The latest CDC data report that there have been about 30,000 cases per year nationwide of the tick-borne Lyme disease, with almost all cases occurring in an 18-state area, including Illinois. The number of those infected appears to be increasing year to year, though not everyone becomes ill.

The most severe manifestations of Lyme disease are arthritis, heart conduction problems or nerve inflammation. Your chance of getting infected with Lyme disease increases if you are bitten by a deer tick or a black-legged tick, or if the tick goes undiscovered and feeds for an extended period of time.

You can protect yourself from ticks by doing the following:

Wear light-colored clothing to better spot a hitchhiking tick.

Wear a hat.

Stay in the center of trails to reduce your chances of brushing against vegetation.

Consider using an insect repellent containing up to 30 percent DEET. A permethin-based product can be applied to clothing, but it has potential for causing skin rashes, so any coated items need to be dry before wearing.

Inspect yourself for ticks after venturing outdoors.

If a tick bites you, remove it as soon as possible by grabbing it as close to the skin as you can with tweezers and pulling the tick out in a straight direction. Do not burn the tick or try to smother it while it is stuck to your skin.

Tick mouth parts left in the skin can cause irritation but do not put you at risk for disease as the main body segment does. Clean the irritated area with soap and water. A red ring rash that spreads outward from the bite site may appear in as soon as three days. This could be indicative of a more serious health problem, so see your doctor as soon as possible. The Fermilab Medical Office will assist with the identification and removal of ticks.

Spring blooms

Particle storage ring to move from New York's Brookhaven Lab to Fermilab in Illinois

From Huffington Post, May 10, 2013

A particle storage ring spanning 50 feet (15 meters) in diameter is set to go on a long cruise this summer, from New York to Illinois, where it will get a new life capturing ultra-rare particles in a magnetic field.

The huge electromagnet, made of steel and aluminum, is the centerpiece of a machine built at Long Island's Brookhaven National Laboratory in the 1990s. Now it's needed at Fermi National Accelerator Laboratory outside of Chicago for a study on muons, exotic subatomic particles that exist for just 2.2 millionths of a second.